1. Field of the Invention
The present invention relates to a packet communicating apparatus in a mobile radio network.
2. Description of Related Art
A mobile network of W-CDMA (Wideband Code Division Multiple Access) is provided with a mobile station (MS), a radio base station (NodeB), a radio network controller (RNC), and a radio packet communication node (SGSN GGSN) (FIG. 11). FIG. 11 is a configuration view of a W-CDMA radio network system.
The RNC and the MS each employ an RLC (Radio Link Control) protocol (3GPP Recommendation TS25.322), in order to effectively carry out a packet communication in a radio block. Then, each of the RNC and the MS has an RLC protocol controller to control the RLC protocol. The RLC protocol controllers of the RNC and the MS carry out the division of packet data at a time of data transmission. Also, the RLC protocol controllers of the RNC and the MS carry out the assembly to the packet data from the divided data at a time of data reception (FIG. 12). FIG. 12 is a diagrammatic view of the division and assembly of the packet data of the RLC protocol. Also, FIG. 13 shows an RLC protocol control block diagram in a conventional technique.
Also, the division size of the packet data defined in the 3GPP recommendation is as follows.                1 to 126 bytes (LI=7 bit)        1 to 32,766 bytes (LI=15 bit)        LI:Length Indicator (Information Length Width)        
Hereafter, the packet data is noted as SDU (Service Data Unit), and the divided data is noted as PDU (Protocol Data Unit). In an RLC protocol process, if a next transmission SDU does not exist within a framed timer when the SDU is divided, a padding area may exist in the final PDU. Here, the framed timer implies a time when a concatenation transmission process is carried out if there is a transmittable next SDU.
The size of the padding area is determined by an SDU length to be transmitted and a PDU length to be divided. Then, when the PDU length is N bytes, there is a possibility of generation of the padding area having a maximum of (N−1) bytes (FIG. 14A and FIG. 14B). FIG. 14A and FIG. 14B is a conceptual diagram showing an example of the generation of the padding area. FIG. 14A shows that the PDU length is 40 bytes, and FIG. 14B shows that the PDU length is 120 bytes.
Since the padding area is needed in the RLC protocol control, it is transmitted by using a radio resource, between the NodeB and the MS. However, the padding area is not finally used in the RLC protocol process and discarded in the RNC and the MS.
The consideration content with regard to the size of the padding area will be shown below. In the current W-CDMA, the SDU up to 1,520 bytes can be transmitted at the downstream maximum of 384 Kbps and at the upstream maximum of 64 Kbps.
If the SDU of 1,500 bytes is averagely transmitted at 300 Kbps from a fixed network side to the MS in which the PDU length is 40 bytes, the RNC carries out the division and transmission of the SDU at a 40 ms period. The PDU number that can be transmitted in 40 ms is 48. That is, if a transmission speed is 384 Kbps, there is a relation of 40 byte×8 bit×1200/sec=384,000 bit/sec. For this reason, 12 PDUs each having 40 bytes can be transmitted in a 10 ms period (FIG. 15A). FIG. 15A and FIG. 15B is a conceptual diagram of the PDU transmission.
Also, the SDU of 1,500 bytes is divided into 38 PDUs from the relation of 1500 byte÷40 byte/1 PDU=37.5 PDU (FIG. 15B). Then, the user data of 20 bytes and the padding data of 20 bytes exist in the final PDU. Then, the transmission of the PDU including the padding data is executed 25 times per second. For this reason, the data in which a total of 500 bytes is discarded is transmitted. Thus, as shown in FIG. 15B, the uselessness occurs in a radio block.                [Patent document 1] JP 2003-179974 A        [Patent document 2] JP 2002-27023 A        [Patent document 3] JP 2001-326647 A        [Patent document 4] JP 2658896        [Patent document 5] JP 2002-30144 A        [Patent document 6] JP 2002-125004 A        